Here's some more information/examples of both. It's worth pointing out that both of these reports can be easily ran on a per item basis by simply right clicking on the item itself inside Item Master Data:

The Inventory Posting List can be used for items, BPs or Other options (tabs at the top left corner). On the item level, you can select a range of item codes, item groups, item properties or just by date range (I used 1/1/16 to 12/31/16 just to give us a good variety of transactions in my test database). On the right side you have the ability to filter down by one or multiple warehouses. In this example I am just going to display the A1 warehouse:

Here you can see every transaction that posted between those date ranges as well as the documents involved for each transaction. Click on the gold arrow next to the item number to drill in to that document and get further information as to what caused the increase/decrease in quantity.

The Inventory Audit Report allows you to filter by posting or system date (or leave blank to not filter date at all) as well as by item code, item group or item properties if you choose. Below that is a list of warehouses. Simply select the warehouse(s) you wish to include and click "OK" to display the results. In this example I am just displaying a list of transactions by item from warehouse A1:

By default everything will be collapsed, but you can click the black right arrow next to any item to expand it, or "Expand" button in the bottom right to expand them all:

Because this is a test database you might notice some strange things (system date quite a bit different than posting date) but it gives you an idea of what the data looks like at least as transactions flow in and out of this warehouse. The "Document" column has a list of documents that caused the increase/decrease in inventory and clicking the gold arrow allows you to drill directly in to that document.

Final note: Any time you see the left arrow and "OK" at the bottom of a page:

Keep in mind that the blue arrow returns you back to the previous window where you can change parameters/rerun the report and "OK" will close both windows.